1. Field of the Invention
The present invention relates to diesel engines of the direct fuel injection type, and more particularly to a combustion construction chamber for such diesel engines.
2. Description of the Prior Art
In conventional diesel engine of the direct fuel injection type, a cavity C having circular shape in cross-section and is formed in the crown of the piston P, and fuel jets are injected toward the preipheral wall w of the cavity C from a multi-orifice fuel injection nozzle N which itself is directed toward the center of the cavity C, as shown in FIGS. 1 and 2.
The the fuel jets impinge the circular peripheral wall w and are distributed in such a manner as illustrated in FIG. 2a by a swirl S which is generated in the cavity in a known manner.
In general, the fuel mixture f.sub.1 distributed at the downstream portion of the swirl S constitutes a lean mixture which is likely to increase unfavorable HC emission due to its poor combustibility. The fuel mixture f.sub.2 is an ideal mixture which presents a good combustion. The fuel mixture f.sub.3 is a too rich a mixture with insufficient air, and leads to emission of CO and smoke.
The above described distribution of injected fuel forming lean mixture f.sub.1, ideal mixture f.sub.2 and rich mixture f.sub.3 is also observed in vertical planes, as seen from FIG. 2b, which would necessarily lead to emission of HC, CO and smoke.
And also mixture flows out from the opening O of the cavity C into space which surrounded by cylinder head H, cylinder liner L and piston P by inverse squish IS which appears after the piston has passed the top dead center. Since the cylinder liner L and cylinder head H are usually cooled by cooling water or the like, the portion of the fuel which is biased to the space is cooled upon contacting those members and turns incombustible whereby the emission of smoke is considerably increased.